BERLIN, April 26 (Reuters) - German and French officials on Thursday pressed ahead with plans to jointly develop a next-generation fighter jet, a drone and a maritime airborne warfare aircraft, saying the projects showed European unity and strength in an increasingly uncertain world.

German Defence Minister Ursula von der Leyen and her French counterpart Florence Parly stood side by side at the ILA Berlin Air Show and hailed the ambitious Franco-German weapons push as "historic" and a key step for European autonomy.

"This is a historic agreement," Parly told a throng of journalists, military officials and industry executives. "It shows that Europe is more than a sum of medium-sized powers, and can take its fate into its own hands and ensure its autonomy."

The ministers signed a letter of intent to explore joint development of a maritime warfare aircraft for use from 2035, a document outlining the high-level common requirements for a new fighter jet, and a concept of operations for a joint training and operation of a fleet of C-130J transport planes.

They also agreed to continue working on a Euro-drone project with Italy and Spain, after three European defence companies unveiled a first full-scale model of their planned Medium-Altitude Long-Endurance (MALE) drone.

The companies - Airbus, Dassault Aviation and Leonardo - said the project underscored their commitment to build a European version of an unmanned aerial system in a world dominated by U.S. and Israeli designs.

But the biggest and most ambitious of the new projects seeks to develop a new manned fighter jet to replace Eurofighter Typhoon and Rafale warplanes beginning in 2040.

The move to develop a new warplane is seen as a preliminary step towards overcoming differences that have left Europe struggling to maintain three competing fighter programmes - France's Rafale, Sweden's Gripen and the Eurofighter, involving Germany, Britain, Italy and Spain.

Von der Leyen said other countries would "naturally" be allowed to join in, but Parly cautioned that requirements for the jet would be set by France and Germany first.

Italy, Spain and Britain have already expressed interest.

Airbus and Dassault on Wednesday signed an agreement to work together on the new project, but avoided saying which of the two aerospace companies would be in charge.

The political documents signed on Thursday revealed continuing differences between Germany and France on how narrowly or broadly to proceed with the fighter and maritime aircraft programmes. It also remains unclear whether the countries will develop a new maritime aircraft, or build on an existing design. (Reporting by Andrea Shalal; editing by Andrew Roche)